Stator Configuration Research Articles

High-turbulence fine particle flotation cell optimization and verification

Microfine mineral particles have a small size, light weight, and low inertia, making it difficult for them to deviate from streamlines and collide with bubbles. Conventional flotation operations consume a large amount of reagents and exhibit poor flotation indicators. This study employs computational fluid dynamics (CFD) simulation and hydrodynamic testing to investigate the flow field within a high-turbulence microfine particle flotation machine equipped with a multilayer impeller–stator configuration, and validates the practical application performance of the microfine particle flotation machine through single-batch flotation experiments. Result shows that the impeller region of the traditional mechanical stirring flotation machine has a turbulent energy dissipation rate of 20 m²/s³, whereas that for the microfine particle flotation machine averages over 120 m²/s³. In the flotation verification, the cumulative recovery rate of the fine particle flotation machine is increased by 28% compared with that of the traditional KYF flotation machine. The flotation rate is also 1.3 times that of the KYF, demonstrating stronger selectivity for fine particle concentrates. It has certain guiding significance for the resource utilization of fine particle minerals.

Development of Carbon Composite Blades within the Context of the Experimental Validation of a CFD-Based Design Tool for Contra-Rotating, Electric Fan Engines

Electric propulsion systems have emerged as a disruptive technological approach towards achieving sustainable and climate-neutral aviation. To expand the operational envelope of such propulsion units in terms of altitude and velocity, an enclosing duct and counter-rotating rotors to enhance efficiency can be utilized. In this study, an iterative CFD-based design tool developed for these novel propulsion systems is utilized to design a reference engine, having a classic rotor–stator configuration. Being the key component of this propulsor, a manufacturing process for composite blades is presented. This effort aims to make state-of-the-art technology accessible to smaller research projects, promoting the widespread adoption of electric propulsion technology in the aviation sector. By experimental investigations of the blade elongation both in tensile tests and engine operation, measuring the tip clearance with a high-speed camera, this process could be validated to facilitate the transferability of research. Finally, the performance of the manufactured engine is measured by a five-hole miniature probe, not only in design point but also in off-design operation. The results indicate that a substantial reduction in discrepancies between initial specifications, subsequent CFD simulations, and experimental investigations compared to conventional design tools relying on empirical formulations can be achieved due to the CFD-based approach. This allows the CFD-based tool to be validated for designing scalable contra-rotating fan engines.

Investigation of shaded pole stator topology for low power AC motors design

PurposeThis paper aims to investigate the features of single phase shaded pole stator with squirrel–cage rotor or permanent magnet rotor, that leads to an investigation of these topoloties as induction motor or synchronous motor. The comparative analysis is realised for the following three topologies: single phase shaded pole induction motor (SPIM) with squirrel–cage rotor, the second topology (single phase synchronous motor) has the same stator configuration but with permanent magnet rotor and the third investigated topology is similar to the second one, where the stator poles instead of iron steel are made of soft composite material.Design/methodology/approachThe investigation in this work starts with a performance analysis of single-phase SPIM. Afterwards for the same stator topology the squirrel rotor is replaced with a two-pole permanent magnet rotor and the same performance analysis is realised for this topology. Finally, the second topology is improved bay replacing the iron steel stator poles with stator poles made of soft magnetic composite material and performance analysis is realised for this third type of topology as well. The performance analysis of all topologies is realised by implementation of finite element method and finite element analysis.FindingsThe presented data and diagrams from the realized investigation show that single phase synchronous motor with shaded pole stator has an improved characteristics in comparison with the initial single-phase SPIM. Finally, the third topology realized on the bases of the single-phase synchronous motor has the best performance characteristics due to the implementation of soft magnetic material in the realization of the stator poles. The proposed methodology for structural and performance improvement of a single-phase SPIM topology opens the possibility for additive manufacturing application and significant cost reduction.Originality/valueThe focus was put on exploration the possibilities of the single-phase shaded pole stator topology for application in low-power and low-cost single phase self-starting motors. By simple replacement of the squirrel–cage rotor, in the reference AKO-16 motor, with one-piece ferrite permanent magnet rotor, the self-starting single phase synchronous motor was derived. In the next step, owing to simplify the SPPM motor production process and manufacturing, the stator poles instead of iron steel lamination were made of soft composite material Somaloy®. It opens the possibility for additive manufacturing application and significant cost reduction.

SSO-DRSS Axial Flux sensing in Switching Permanent Magnet Motor for cogging torque mitigation

This paper addresses the imperative requirements of high efficiency, power density, and speed in Axial Flux-Switching Permanent Magnet Motors (AxFSPM) for electric vehicles. Recognizing the limitations of conventional motor designs, especially their weight and size, hindering their universal applicability, this study proposes a novel approach. A Double Rotor Single Stator (DRSS) configuration is introduced, and its parameters are systematically optimized using the Shark Smell Optimization (SSO) algorithm. The SSO algorithm refines critical motor parameters, including axial length, turns per phase, and stator and rotor dimensions, resulting in a more compact AxFSPM motor with enhanced torque. Geometrical constraints are similarly optimized with SSO, and magnet skewing angles are employed for cogging torque reduction. The optimization process, implemented in MATLAB and ANSYS Maxwell, yields an average torque below 1.4 N m and cogging torque below 0.8 N m, demonstrating the effectiveness of the proposed approach. Comparative analyses against various motor models underscore the superiority of the SSO-optimized DRSS motor in terms of efficiency and compactness.

Material Tradeoff of Rotor Architecture for Lightweight Low-Loss Cost-Effective Sustainable Electric Drivetrains

The art of the successful design of high-speed electrical machines comes with many challenges in the mass, size, reliability, and energy efficiency. Material engineering of electrical machines has been identified as a key solution for higher power dense electric drivetrains. One of the main challenges at high speed is the eddy-current losses in the active electromagnetic parts, especially magnetic materials and permanent magnets (PMs). This study is devoted to the selection of PM rotor materials using multidisciplinary design optimization for a high-speed electric drivetrain. Beside AC loss minimization, more disciplines are considered, such as the minimization of weight, and cost. Different laminations are investigated with different magnetic properties as well as cost. Additionally, different PMs are optimized considering low-cost ferrite and high-coercivity permanent magnets (HCPMs). Moreover, the optimal materials are identified which have the best balance between loss, weight, cost, ripples. Finally, different rotor designs are prototyped, assembled, and tested using the same stator configuration. Also, the best rotor design is selected, and the electromagnetic performance is measured and compared with conventional designs. The optimal design results in 8% extra torque with at least 20% weight reduction.

Molecular Turnstiles Featuring Bicyclic Rotators: Solution and Solid‐State Investigation of Steric and Electronic Concerns

AbstractA molecular rotor is created when a 2,1,3‐benzothiadiazole rotator is incorporated into a rigid arylene ethynylene framework supported by pyridine coordination to a metal (Ag+ or PdCl2) guest. Comparisons to a similarly sized naphthyl rotator via 1H NMR spectroscopy provide insights into the movement of these bicyclic rotators relative to the rigid stator framework. Chemical shift increases of 0.3 ppm, or more, upon metal complexation are consistent with through‐space interaction of the central arene with a bound PdCl2 guest. Further study via X‐ray crystallography illustrates that rotation of the 2,1,3‐benzothiadiazole unit in the solid state is likely hampered by relatively strong chalcogen bonding (N⋅⋅⋅S distance of 2.93 Å), forming 2S‐2N squares between benzothiadiazoles of neighboring complexes. Strong π–π interactions (3.29–3.36 Å) between neighboring complexes likewise restrict solid‐state rotation of the potential benzothiadiazole rotator. Modest changes to UV–vis spectra upon metal coordination suggest that electronic properties are mostly independent of stator configuration.

Large Eddy Simulation of Externally Induced Ingress about an Axial Seal by Stator Vanes

Turbine inlet temperatures in advanced gas turbines could be as high as 2000 °C. To prevent ingress of this hot gas into the wheelspace between the stator and rotor disks, whose metals can only handle temperatures up to 850 °C, rim seals and sealing flows are used. This study examines the abilities of large eddy simulation (LES) based on the WALE subgrid model and Reynolds-averaged Navier–Stokes (RANS) based on the SST model in predicting ingress in a rotor–stator configuration with vanes but no blades, a configuration with experimental data for validation. Results were obtained for an operating condition, where the ratio of the external Reynolds number to the rotational Reynolds number is 0.538. At this operating condition, both LES and RANS were found to correctly predict the coefficient of pressure, Cp, located downstream of the vanes and upstream of the seal, but only LES was able to correctly predict the sealing effectiveness. This shows Cp by itself is inadequate in quantifying externally induced ingress. RANS was unable to predict the sealing effectiveness because it significantly under predicted the pressure drop in the hot gas path along the axial direction, especially about the seal region. This affected the pressure difference across the seal in the radial direction, which ultimately drives ingress.

Experimental Modal Analysis of Stators Analyzing the Effects of Lamination and Winding

Abstract This paper addresses the experimental analysis of different stator configurations of an electric motor typically used within the automotive sector. The ongoing electrification of the automotive sector, combined with a desire to increase virtual prototyping, means that engineers are increasingly facing new challenges. Against this background, the numerical models of electric motors, particularly stators, are simplified and homogenized. However, this procedure must be supplemented by experimental data to ensure the high quality and reliability of the simulations. Unfortunately, broad experimental investigations are time-consuming and expensive, underlined by the lack of corresponding literature. For this reason, four different stator configurations were investigated as part of the experimental modal analysis to highlight the influence of the stator lamination as well as the winding. The results provide the scientific community with a broad outline of how specific influences change modal parameters of each stator configuration. In particular, the results show that lamination significantly reduces axial stiffness. Highlights of the findings relate to the mode-dependent stiffness, mass, and damping influences due to the winding, with the influence of the stiffness deviating significantly from expectation. It was also found that the selected winding technology dominates the structural dynamic system characteristics. Therefore, it is advisable to include the manufacturing technology intended to be used for the lamination and the winding in the early simulative design phase to improve the model prediction quality.

Circulating and Eddy Current Losses in Coreless Axial Flux PM Machine Stators With PCB Windings

Printed circuit board (PCB) stators in coreless axial flux permanent magnet (AFPM) machines have been proposed, designed, and studied for use in multiple industries due to their design flexibility and reduction of manufacturing costs, volume, and weight compared to conventional stators. This paper investigates mechanisms and methods of approximating open circuit losses in PCB stators within example wave and spiral winding topologies for a dual rotor, single stator configuration using 3D FEA, analytical hybrid techniques and experiments. The effect of rotor magnet shape, end winding, and active conductor geometry on eddy currents is studied, and some mitigation techniques are proposed. Through stator equivalent circuit analysis, circulating current losses caused by mechanical abnormalities and magnetic circuit asymmetry are assessed. Possible strategies and schemes to minimize circulating current losses are also described. The trade-off between stator loss components and some practical design considerations are outlined in detail. The open circuit power losses of a prototype coreless AFPM motor were experimentally tested using multiple example PCB stators and emulated rotor asymmetries, with the findings being comparable to the FEA and hybrid analytical methods results.

Large Eddy Simulation of Rotationally Induced Ingress and Egress around an Axial Seal between Rotor and Stator Disks

In gas turbines, the hot gas exiting the combustor can have temperatures as high as 2000 °C, and some of this hot gas enter into the space between the stator and rotor disks (wheelspace). Since the entering hot gas could damage the disks, its ingestion must be minimized. This is carried out by rim seals and by introducing a cooler flow from the compressor (sealing flow) into the wheelspace. Ingress and egress into rim seals are driven by the stator vanes, the rotor and its rotation, and the rotor blades. This study focuses on the ingress and egress driven by the rotor and its rotation. This is carried out by performing wall-resolved large eddy simulation (LES) around an axial seal in a rotor–stator configuration without vanes and blades. Results obtained show the mechanisms by which the rotor and its rotation induce ingress, egress, and flow trajectories. Kelvin–Helmholtz instability was found to create a wavy shear layer and displacement thickness that produces alternating regions of high and low pressures around the rotor side of the seal. Vortex shedding on the backward-facing side of the seal and its impingement on the rotor side of the seal also produces alternating regions of high and low pressures. The locations of the alternating regions of high and low pressures were found to be statistically stationary and to cause ingress to start on the rotor side of the seal. Vortex shedding and recirculating flow in the seal clearance also cause ingress by entrainment. With the effects of the rotor and its rotation on ingress and egress isolated, this study enables the effects of stator vanes and rotor blades to be assessed.

Detailed Simulations of a Three-Stage Supercritical Carbon Dioxide Axial Compressor with a Focus on the Shrouded Stator Cavities Flow

This paper describes the findings of detailed simulations performed to investigate the impact of seal teeth cavity leakage flow on the aerodynamic and thermal performance of a three-stage supercritical CO2 axial compressor. The study compares a shrouded stator configuration (with cavities) to a cantilevered stator configuration (without cavities) to highlight their differences. High-fidelity computational fluid dynamics simulations were performed using non-linear harmonic (NLH) and mixing plane assumptions, considering various possible rotor/stator interface configurations for mixing plane calculations. The key performance parameters for each case were compared, and the best-performing configuration selected for further analysis. The individual stage performance parameters are also examined and compared between the cantilevered and shrouded configurations. It was observed that in the shrouded case, the leakage flow enters the cavity downstream of the stator trailing edge and gets entrained into the primary flow upstream of the stator, leading to boundary layer changes at the hub and degradation of stator and downstream rotor performance. Vortical flow structures were also observed in the stator wells, which tended to change the flow angles around the region, thereby affecting mixing and velocity distribution, resulting in a slight deterioration of compressor performance. Additionally, the study examines windage heating due to shear work from rotating walls, including the seal teeth surface. The amount of shear work done on the leakage flow and the corresponding rise in fluid temperature were quantified, tabulated, and further compared with a simple analytical model, showing good agreement between them and, hence, validating the numerical approach used.

Slot opening displacement technique for cogging torque reduction of axial flux brushless DC motor for electric two-wheeler application

Introduction. Reduction of cogging torque is the crucial design consideration of axial flux brushless DC (BLDC) motor, particularly for low-speed applications. Aim. The slot opening displacement technique is presented in this article to reduce cogging torque in axial flux BLDC motors suitable for electric two-wheeler applications. Methods. Double rotor single stator configuration of axial flux BLDC motor is the most suitable for such vehicular applications. Initially double rotor single stator 250 W, 150 rpm axial flux BLDC motor is designed with stator slot opening in middle position and considered as reference motor for further analysis. To evaluate the cogging torque profile of the reference motor 3D finite element modeling and analysis are performed. The design is enhanced by dividing all stator teeth into groups and displacing the slot openings of each group in opposite direction with respect to the adjacent group. Results. The influence of slot opening displacement on cogging torque is evaluated with finite element modeling and analysis. As cogging torque is reduced from 1.23 N×m to 0.63 N×m, the slot opening displacement technique is found to be effective in reducing cogging torque of axial flux BLDC motor.

Experimental and numerical study of stator end-winding cooling with impinging oil jet

As an efficient cooling technology, impinging jet was utilized to reduce end-winding temperature of electric machine stator in this study. Infrared imaging and numerical simulation technologies were applied to investigate heat dissipation efficiency of silicone oil jet on a real electric machine stator. Infrared camera is possible to measure end-winding temperature without influence on flow pattern and heat exchange. Numerical simulation results for end-winding temperature were validated by comparing to experimental results. Then heat transfer coefficient was calculated by inverse method, which is very difficult to be obtained by experimental method. The testing stator had three configurations, among which one was covered by aluminum foil at external surface and the other one had extra internal surface in order to lead oil flow to contact all the end-windings. Moreover, effect of dissipated heat quantity and oil flow rate were considered in present study. According to experimental and simulation results, the configuration with internal surface reveals best cooling performance by impinging oil jet. For this stator configuration, the minimum and the most cost-effective oil flow rates were found which will provide insight for impinging jet system.

Cantilevered Tandem Stator in Annular High Speed Test Rig

The present paper investigates the aerodynamic performance of a cantilevered tandem stator based on experiments conducted within a high speed annular test rig at the Technische Universitaet Berlin. A tandem blade in this context describes a double rowed stator configuration where the turning of the incoming flow is split up between two blades arranged in succession. For evaluation purposes, a conventional single bladed stator is used as reference. To provide machine relevant boundary conditions of cantilevered stator assemblies, the moving hub wall is recreated by a rotating disk. Overall, the tandem stator is able to achieve higher flow turning while keeping the total pressure losses below those of a single stator. It is found that the tandem stator in general behaves similar to the conventional stator. When installed in cantilevered fashion, both stator types benefit considerably in terms of loss reduction. Without the hub clearance and therefore absence of the clearance flow, each of the configurations suffered from severe corner separation. The tandem stator responds more sensitively to change in clearance height.

A Cogging Torque Minimization Procedure for Interior Permanent Magnet Synchronous Motors Based on a Progressive Modification of the Rotor Lamination Geometry

This article describes a simple cogging torque minimization procedure for interior permanent magnet synchronous machines (IPMSMs), consisting of a progressive modification of the rotor lamination geometry. This procedure can be generalized for the main topologies of PMSM, independently of the number of stator slots or the location of the permanent magnets. For this purpose, a basic IPMSM structure is analyzed by means of the FEM (finite element method) approach, and then, several other IPMSM geometries, obtained by adequately modifying the rotor lamination geometry of the basic IPMSM model without changing its stator configuration, are proposed and discussed. The trends of the cogging torque generated by each model are computed and compared. From this comparison, it is demonstrated that, by simply acting on the shape of the rotor lamination and by choosing the optimized pattern, the cogging torque components can be theoretically canceled.

Comparative Analysis and Design of Partitioned Stator Hybrid Excitation Axial Flux Switching PM Motors for In-Wheel Traction Applications

A comparative study of new partitioned stator hybrid excitation axial flux switching permanent magnet (HEAFSPM) motors with different partitioned excitation stator topologies for in-wheel traction applications is presented in this paper. The realization approaches of the partitioned stator HEAFSPM motor are discussed, and the motor topology with windings and permanent magnets (PMs) separately setting on different stators is selected in view of the advantageous structure for thermal management. On this basis, two partitioned excitation stator topologies including C-type tooth core and T-type tooth core stator configuration are proposed, and the air-gap flux modulation and flux regulation principle of the motors are analyzed. In addition, the design method of the partitioned stator HEAFSPM motor considering the effect of hybrid excitation sources is provided, and the two motors with different tooth cores are designed respectively. Meanwhile, for a fair comparison, the multiple objectives optimization method coupled with the sensitivity analysis is employed to optimize the two motors. The electromagnetic performances, anti-demagnetization capability, and flux regulation performance of the two motors are all investigated in detail. Finally, two prototype motors are fabricated and tested. Both the theoretical analysis and experimental results verify the effectiveness and reasonability of the motor.

Transient nature of secondary vortices in an axial compressor stage with a tandem rotor

An efficient and compact design of a compressor continues to be a challenging area of research. The unavoidable streamwise adverse pressure gradient together with passage transverse pressure gradient restricts the maximum allowable blade turning. Tandem blading is an interesting concept for increasing the pressure rise by permitting a higher blade turning angle. The energized flow through the tandem blade nozzle gap helps to minimize the possibility of flow separation over the suction surface of the aft blade. However, a coherent transient analysis of a tandem rotor stage in an axial compressor is yet to be well explored. In the present paper, the complex flow field over a tandem rotor and the succeeding stator passage is analyzed in detail. Although the tandem rotor increases the flow turning and diffusion effect, the presence of separate trailing edge wakes and hub corner vortex causes early onset of flow separation over the stator suction. The flow structures developed within the rotor and the stator passages at different time instances are highlighted with the help of limiting streamlines and iso-surface Q-criterion superimposed with entropy contours. The results indicate that within the rotor passage, transient flow features are observed near the hub corner region close to the aft blade trailing edge rather than the tip region. When the rotor passes the stator leading edge, the rotor trailing edge leakage flow at the hub is entrained into the stator leading edge reverse flow region. This is then further circumferentially dragged into the mid-passage region. The interference of multiple rotor wakes with the stator leading edge leads to the formation of longitudinal and arch like separation vortices at the stator-hub and the stator-casing regions, respectively. These separation vortices grow in size while being convected downstream. Eventually, as time progresses, the vortices split and shed periodically from the stator surface. The present investigation highlights the requirement of a new stator design in a tandem rotor–conventional stator configuration. Such designs could further magnify the significant aerodynamic performance obtained using a tandem configuration.

The effect of the PSS configuration on the hydrodynamic performance of the KP505 propeller behind the KCS

The presented paper has numerically investigated a new pre-swirl stator (PSS) configuration on a ship propulsion performance. The KP505 propeller and the KRISO container ship (KCS) are used, and the PSS is installed before the propeller to adjust wake inflow and increase the performance of the propeller. To simulate PSS in front of the propeller, the STAR-CCM + solver (computational fluid dynamics) is used. First, the hydrodynamic characteristics of the model propeller KP505 results are compared with the available measurements and experimental data with relatively good agreement. Then, the flow over the KCS is simulated, and its wake flow is captured. This wake flow is entered into the propeller with and without PSS. The present paper introduces a new PSS configuration with eight blades, and the angle of attack of 15° is modelled and mounted in front of the propeller. The thrust and torque coefficients at four advance coefficients (between 0.24–0.91) are presented and discussed. The numerical results indicate that the PSS with these parameters works well in the low ship speed and increases efficiency and decreases delivered power. Also, the PSS's effect reduces the pressure fluctuation by 16.48% in the backside of the propeller blade.

Design of External Rotor Ferrite-Assisted Synchronous Reluctance Motor for High Power Density

The rare-earth (RE) permanent magnets (PM) have been increasingly adopted in traction motor application. However, the RE PM is expensive, less abundant, and has cost uncertainties due to limited market suppliers. This paper presents a new design of a RE-free five-phase ferrite permanent magnet-assisted synchronous reluctance motor (Fe-PMaSynRM) with the external rotor architecture with a high saliency ratio. In such architecture, the low magnetic coercivity and demagnetization risk of the ferrite PM is the challenge. This limits the number of flux barriers, saliency ratio, and reluctance torque. A precise analytical design procedure of rotor and stator configuration is presented with differential evolution numerical optimizations by utilizing a lumped parameter model. A 3.7 kW prototype is fabricated to validate the proposed idea.

Interacting Effects in a Multistage Axial Compressor Using Shrouded and Cantilevered Stators

This paper describes the analysis of the flowfield in a four-stage low-speed axial compressor at the design point investigated both numerically and experimentally, with particular emphasis on the impact of stator hub flow leakage in a section of the machine featuring a change of stator configuration. The goal of the work is to give insight into the effect of the stator hub configuration on the aerodynamic performance in terms of loss and efficiency of downstream blade rows as well as the resulting stage matching effects. The investigation is focused on aerodynamic behavior and stage interaction, which the stator hub configuration of a given stage induces in a downstream stage with respect to its performance and flowfield. Two shrouded and one cantilevered stator hub configurations, such as those commonly employed in industry, are investigated and discussed with respect to local flow phenomena and stagewise aerodynamic effects. The results show that the stator hub configuration of a given stage has a drastically high impact on the downstream rotor aerodynamic performance, whereas the downstream stator as well as the upstream rotor are only slightly influenced by the stator hub configuration.